In 2008, the US government released its first physical activity recommendations about the types and amounts of physical activity that offered substantial health benefits to all Americans. The guidelines were based, in part, on epidemiologic studies of health outcomes, including all-cause and cardiovascular (CVD) mortality. However, those studies relied mainly on self-reported physical activity. Self-reported measures, such as questionnaires, are limited in detecting activity that is common and interspersed throughout the day, such as unstructured or unplanned activities, as well as activity that is light or sedentary. By contrast, accelerometers provide an objective measure of physical activity and sedentary behavior. To our knowledge, there are no published epidemiologic studies of the association between objectively measured physical activity or sedentary behavior with CVD. This proposal is in response to the Program Announcement (PA-09-244) Nutrition and Physical Activity Research to Promote Cardiovascular and Pulmonary Health (R21). Using a population- based diverse sample of adults, we address the program announcement high priority areas by (1) utilizing objective measures of physical activity with accelerometry and (2) including understudied and representative populations. Using the adult sample of participants enrolled in the National Health and Nutrition Examination Survey (NHANES) from 2003-06 (n=9142), we will determine the associations of objectively-assessed physical activity and sedentary behavior with the risk of all-cause and CVD mortality. Our secondary aims include (1) using latent class analysis to determine patterns of objectively-assessed physical activity and determine the association of these patterns with the risk of all-cause and CVD mortality and (2) determining the association of self-reported physical activity with the risk of all-cause and CVD mortality, and contrast the resulting associations with those found using objectively-measured physical activity. For the NHANES cohort, physical activity was determined using both a self-reported assessment and an objective measure, the ActiGraph accelerometer. The accelerometer accurately detects movement that can be translated into sedentary, light, moderate, and vigorous physical activity. Participant files will be linked with mortality through 2009 using the National Death Index (NDI). We have sufficient power to detect associations between physical activity and all- cause and CVD mortality. Results from the proposed cost-effective study can provide evidence towards the national physical activity guidelines with more specificity related to physical activity and sedentary behavior and greater generalizability, because NHANES includes a representative sample of US adults.